In association with the aging of the US population, there is a projected increase in the prevalence of many diseases, especially cardiovascular diseases and stroke. While the incidence of stroke has shown a steady and gratifying reduction in recent years, the absolute number of stroke survivors is increasing steadily and will continue to increase into the foreseeable future. It follows that the projected economic, human, and social costs of such illnesses will constitute an increasing burden for society. Given these projections, robotic devices designed to improve the efficacy, accessibility, and cost of stroke rehabilitation are likely to become both socially important and commercially viable. Intelligent Automation, Inc. (IAI) proposes to develop a robot-based three-dimensional rehabilitation environment for training upper limb movements following stroke. The proposed work builds on the previous development and preliminary research using the MACARM - the Multi-Axis Cartesian-Based Arm Rehabilitation Machine. The MACARM is a unique cable robot that provides 6 degrees-of-freedom of motion, a large work volume, high stiffness and force capacity, and a high level of positional and force measurement accuracy. IAI will be working closely with researchers at the Rehabilitation Institute of Chicago (RIC). The RIC is one of the premier rehabilitation institutes and is a major center for research in robot-assisted rehabilitation. The existing prototype MACARM device is currently located in the RIC, where it is undergoing functional evaluation as part of an ongoing NIDRR-funded project. The proposed Phase I project will focus on further technical development of the MACARM in preparation for clinical testing, which will take place in Phase II. The specific aims for this Phase I SBIR are: to develop software-based compensation for gravity loading of the upper limb using the MACARM; to implement an enhanced visual display of workspace for training reaching movements and for providing motivating feedback to patients; to evaluate options for collection of joint space data within the MACARM; to identify and address the software and hardware modifications necessary for the MACARM to be evaluated in a clinical environment; and to design the clinical research study to be performed in Phase II. Currently in the United States there are over 4.7 million stroke survivors, with approximately 750,000 people suffering a new or recurrent stroke each year, making it the leading cause of disability in the US. The proposed work on the development of a novel cable robot for upper limb rehabilitation will ultimately lead to an improved quality of living for those affected by restriction of upper limb motion due to stroke. Additionally, the findings of the proposed research are expected to have important implications for the rehabilitation of arm function in other patient populations, particularly those with cerebral palsy and traumatic brain injury. [unreadable] [unreadable]